problem with cylinder head

[doug440]

riding and the sled just slowed and couldn't get it to start again. after it sat awhile it seemed like it wanted to, but the more you pulled worse it got even after ether in the plugs. spark was still good too. pulled the heads and this is the right side cylinder, part of the ring is missing, but was caused this type of wear?

[mswyka]

What do your spark plug and the underside of the head look like?  My first inclination is to say that your engine was running too lean, but the pattern is different than what I have seen happen on my invader.  Normally I see a divot just downstream of my spark plug and then a sputter type deposit on everything.  In this case it almost looks more like metal fatigue failing the part of the piston that retained the ring and then  the ring broke up and beat up the top of the engine.  Probably still driven by a lean condition - perhaps not quite so lean as what I have been experiencing.

[doug440]

put new plugs in so cant tell by the plugs, ones i took out looked not bad either, but the underside of the head looked eaten up like this also. running br9es(?) thought it was weird since it ate all the way down to the ring nearly. my suspicion was it burnt thru but i found this. other side was fine, nothing odd at all. think maybe bad oil injector? 

[Joel]

Usually when the ring landing goes, it is a sign of coolant coming in the cylinder (leaky fire ring) but I'm not very familiar with the Invader engine.Only speaking from experience with the monohead liquid motors.Joel

[Joel]

Basically the ring landing piece was floating or beating up the piston and head.

[Checkmarks]

That is not piston wear.  Your picture is what gets called 'piston failure'. When aluminum (piston top) melts and flows out the exhaust port there are a variety of faces painted on piston faces.  You say one piston (PTO) side looks good and this one smiles from the MAG side, I wonder what it could be.  See I really do not know yet, but lets investigate.

1.  Did you change your crank case seals?
2.  Are the proper clean jets in your carburetor with air box?

Guess, guess, guess.  Pull the motor it takes about 30 minutes.  Disassemble (so you can put in new crank seal) and report back with a picture of the Mag side seal.  I suspect you will find your answer.